Muffle-type gas-fired self-cleaning oven

ABSTRACT

A self-cleaning gas oven having separated cooking and heating compartments in which the smoke and odor-containing gases from the cooking compartment are mixed with the air required for the combustion of fuel and passed into the heating compartment so that smoke and odor components are incinerated by the combustion process.

Re t'ren cesfii ted UNITED STATES PATENTS Esher R. Kweller Downers Grove; Robert B. Rosenberg, Evergreen Park;

United States Patent [72] inventors 126/21 AX 126/299 A 126/21 A 126/21 A 126/21 A 126/21 AX In M W] nu n n "I d H n l "y e fls LW S .f eu o SHHPPT 898899 3x3 mmwmmm 579250 wnwnwm 2 8 6 J 0 60 8 1 1 223333 U f 0 m k m v. N g 0 h k 0 .m m H c e m T m in L %Wt un- 1.10 979 mum 2 t 6 D8001. 0 de N 6e Mm d .l Wows Ha AFPA 1111. 253 22M7 1.1 .1

[54] MUFFLE-TYPE GAS-FIRED SELF-CLEANING OVEN ABSTRACT: A self-cleaning gas oven having separated cooking and heating compartments in which the smoke and odorcontaining gases from the cooking compartment are mixed with the air required for the combustion of fuel and passed 126/21, 21 mto the heating compartment so that smoke and odor com- A, 299, 299 A, 299 B ponents are incinerated by the combustion process.

14 Claims, 3 Drawing Figs.

[51] lnt.C1............... [50] FieldofSearch............................................

MUFFLE-TYPE GAS-FIRED SELF-CLEANING OVEN BACKGROUND OF THE INVENTION oven disclosed in the Huebler et al. patent. The disclosure of Huebler et al. U.S. Pat. No. 3,416,509, insofar as itprovides background discussions pertinent to the present invention,is hereby incorporated by reference.

Heretofore, the'pn'ncipal difficulties encountered in the construction of self-cleaning ovens have been the large amount of time and heat needed to clean the oven, the large amount of heat rejected by the cleaning process into the kitchen or the space in which the oven is located, and the smoke and odor generated by the cleaning process. These difficulties have been solved by the self-cleaning gas oven disclosed in Huebler et al. U.S. Pat. No. 3,416,509. The present invention is an improvement over the self-cleaning gas oven of Huebler et al. in that smoke and odor are further positively eliminated by direct burning or incineration prior to discharge from the oven.

It is, therefore, an object of the present invention to provide an improved self-cleaning gas oven.

Another object of the present invention is to provide a selfcleaning gas oven which discharges combustion products from the cleaning cycle into a room at relatively low temperatures.

It is still another object of the present invention to provide'a self-cleaning gas oven which positively eliminates smoke and odor in the gaseous stream exhausted into the kitchen by means of direct incineration or burning.

Further objects of the invention can be gathered from the following detailed description.

SUMMARY OF THE INVENTION In accordance with the present invention, we provide an improved self-cleaning gas oven which has separated cooking and heating compartments, wherein the smoke and odor containing gases issuing from the cooking compartment are mixed with the air required for the combustion of fuel and passed into the heating compartment for burning with the fuel gas to incinerate the smoke and odor components in the gases.

BRIEF DESCRIPTION OF THE DRAWINGS AND OF THE PREFERRED EMBODIMENT The objects of the present invention are achieved by providing a selflcleaning gas oven in which the exhaust gases from the cooking compartment are incinerated at relatively high temperatures prior to discharging from the oven so that smoke and odor components in the exhaust gases are thoroughly eliminated. The incineration of the exhaust gases from the cooking compartment can be best achieved by providing separate cooking and heating compartments in the oven, and passing the exhaust gases from the cooking compartment to the heating compartment for contact with the burners prior to discharge from the oven. In this manner, substantially no gases will be discharged from the cooking compartment of the oven directly to the exterior of the oven without passage through the burner section of the oven.

The invention will now be described in detail in connection with the drawings, in which: a

FIG. I is a schematic sectional view illustrating a preferred embodiment of the oven of the present invention;

FIG. 2 is aschematic sectional view illustrating another embodiment of the oven in the invention; and

FIG. 3 is a schematic view showing the heat regeneration device illustrated in FIGS. 1 and 2.

Referring to FIG. 1, a self-cleaning gas oven in accordance with the present invention is generally shown at 10. Oven 10 is surrounded by an insulating layer II to prevent leakage of heat into the kitchen. Oven 10 has a top surface 12 on which conventional burners and stove units may be placed. The oven 10 is generally divided into a cooking compartment 13, a heating compartment 14, conduit 15 for exhausting combustion products from the oven, and conduitl6for admitting air into heating compartment 14 for supporting the combustion fuel therein. A suitable fuel gas is supplied from a source 17 through conduit means l8'into an orifice l9 and to burner element 20. The fuel gas is mixed at orifice I9 with air from conduit 16 for burning at burner element 20. Oven I0 has an upper door 21 for access to cooking compartment 13 and a lower door 22 for access to a broiler pan 23 located in heating compartment 14 below burner element 20. Air for supporting combustion at-burnerelement 20 is supplied by means of a fan 24 through a heat regeneration device 25, to be described below, into conduit 16. The combustion products from burner element 20 are circulated byway of conduit 15 around the cooking compartment 13 to thereby heat the same and exhausted through the heat regeneration device 25 by fan 26. The heat regeneration device 25 is rotatably mounted and driven by a motor-27.

An opening 28 nearthe front bottom of cooking compartment l3 isrprovided to admit a small amount of ambient air into cooking compartment 13 to aerate the same. The amount of this aerating air is relatively small and can be varied. We prefer to use an amount of this aerating air as compared to the airsupplied to the heating compartment, of about 1:5 to 1210. Opening 28 is relatively small and does not obstruct the flow of combustion products in conduit 15. The air and vaporized soil from. cooking compartment 13 leaves that compartment via opening 29 located adjacent to the conduit 16 for admitting air to support combustion of burner 20. Conduit 16 forms into a venturi shape at about thepoint it meets opening 29 so as to aspirate the gases from cooking compartment I3. In this manner, the gases from cooking compartment 13 are drawn out of that compartment and mixed with incoming air and passed on to burner element 20 for combustion thereat.

The combustion products from the burning of fuel and other gases at burner element 20 are conducted around cooking compartment 13 via conduit I5 so that heat is transferred from the hot combustion products to cooking compartment 13. As shown in FIG. 1, conduit 15 includes a portion formed on the inside of door 21. In this manner, cooking compartment 13 is evenly and thoroughly heated by the hot gases passing through enveloping conduit 15. However, it is not necessary to provide for the heating at the door to the cooking compartment.

The heat regeneration device 25, which has been described and shown in more detail in said Huebler et al. U.S. Pat. No. 3,416,509, is rotated slowly by motor 27 to transfer heat from the hot combustion products in conduit 15 to the incoming air in conduit 16. Regenerator 25 accomplishes this result by acting as a heat sink so that heat is transferred from the hot gases in conduit 15 toregenerator 25, and then when the hot portion of the regenerator 25 is rotated to be in contact with the cool air in conduit 16, heat is transferred from regenerator 25 to the relatively cool air. Although the embodiment shown in FIG. 1 employs a heat regenerator, the use of a tube and shell or finned heat exchanger in place of the regenerator 25 is also contemplated.

The heat regeneration device is preferably of corrugated or honeycomb design which permits the passage of gases therethrough. It may be made of heat-resistant material which has a high heat capacity. Examples of suitable materials for this purpose are asbestos impregnated with sodium silicate or a ceramic or refractory material.

As can be gathered by comparing the foregoing with the disclosure of Huebler et al. U.S. Pat. No. 3,416,509, the principal feature of the present invention is the collection and injection of the soil-laden gases from the cooking compartment 13 into the air stream to be fed to the burner element 20. The advantages flowing from the present invention are the most complete oxidation and elimination of smoke and odor-carrying components in the gases exhausted from the oven while at the same time retaining the low-exhaust gas temperature realized by the invention of Huebler et al. In the oven-cleaning cycle, a temperature of 750-l000 F. or II F. is typically realized in the cooking compartment of the oven. Such high temperatures are usually sufficient to oxidize most of the soil in the oven and to vaporize the remaining soil. However, there is the possibility that extremely fine grease or smoke particles, containing incompletely oxidized materials, may be suspended in the gaseous stream and be exhausted into the kitchen. The presence of such fine smoke and grease particles, aside from its immediate objectionable efi'ects on persons in the kitchen, will tend to deposit on the walls and furniture in proximity to the oven and eventually permeate through the house. It is the object of the present invention to eliminate, as completely as possible, the presence of such smoke and odor carrying components in the exhaust gases from the oven.

FIG. 2 shows another embodiment of the oven of the invention. The embodiment shown in FIG. 2 is generally similar to that shown in FIG. 1, except that the heat regeneration device 25 is of a modified design (as shown in FIG. 3) and the exhaust gases from cooking compartment 13 are mixed with incoming air prior to the airs passage through the heat regeneration device 25.

Referring to FIG. 3, the modified heat regeneration device 3I is shown to be constructed in a substantially annular and cylindrical form having a central opening 32. At the center of opening 32, there is a shaft 33 supported on bearing members which are in turn connected to the inner annular wall 34 of regenerator 31 by means of spokes 35. As shown in FIG. 2, the hot combustion products in conduit 15 are passed through the regenerator 31 at its upper portion. The gases exhausted from cooking compartment 13 are passed through the upper half of opening 32. After passing through opening 32, the exhaust gases from cooking compartment 13 are then mixed with the incoming air by fan 24 and go through the lower portion of regenerator 31 with said air. The lower half of opening 32 in the regenerator 31 is closed off by baffle means 36 attached to the bearings supporting the shaft 33. In this manner, the incoming air is prevented from bypassing the heat regenerator 31 by going through the lower half of opening 32.

It can be seen from the above that the embodiment shown in FIG. 2 differs from that shown in FIG. I primarily in that the exhaust gases from cooking compartment 13 are mixed with the air supplied to burner element before the air passes through the heat regeneration device. In FIG. 2, the opening 32 is provided in heat regenerator 31 so that the hot exhaust gases from cooking compartment 13 will not leave condensed smoke or odor carrying particles in the regenerator. Once the exhaust gases from cooking compartment I3 have been mixed with the relatively cool air, the combined gas stream is at a relatively low temperature and will be heated by regenerator 31 so that no substantial condensation can take place during the passage of the mixed gaseous stream through the heat regenerator. However, the embodiment shown in FIG. I is preferred since it is simpler and a more direct method for achieving the desired result.

The invention will now be described with reference to a particular example.

EXAMPLE A muffle-type self-cleaning oven generally similar to the oven shown in FIG. I, was operated under the following conditions. The over was preheated for about 20-30 minutes with a total heat input of about 7,l00 B.t.u. to raise the temperature in the cooking compartment 13 to about 800 F. Thereafter, heat input to the oven was continued at a rate of about 6900 B.t.u. per hour for the cleaning cycle. When steady state was reached, the following temperatures were found in various portions of the oven. The cooking compartment 13 was at about 800 F.; the conduit'lS had an average temperature about [060 F.; fresh air entering conduit I6 had a temperature about 75 F.; preheated air after passing through the heat regeneration device 25 had a temperature about 758 F.; preheated air after mixing with the gases from the cooking compartment 13 had a temperature about 765 F.; the temperature of exhaust gases entering heat regeneration device 25 had a temperature about 830 F. and the temperature of exhaust gases leaving the heat regeneration device had a temperature of about 285 F. The above temperatures were found for a heat regeneration device 25 in the form of a wheel with a 7-inch diameter and 2 inches thick. With a wheel 3 inches thick, an exhaust temperature about 230 F. may be obtained. Fresh ambient air was introduced into conduit 16 at the rate of about 12.4 pounds per hour. Air introduced into cooking compartment 13 by way of opening 28 was at the rate of 2.3 pounds per hour. The entire cleaning cycle took a little over 2 hours. The exhaust gases from the oven were substantially free of smoke and odor containing particles.

The self-cleaning gas oven of the invention can be made to be convertible into a convection oven by providing baffle means operable to pass the hot combustion gases from the heating compartment directly into the cooking compartment and thence to the heat regeneration device. In that case, of course, the opening 29 in FIG. I for recycling the gases from the cooking compartment back to the heating compartment must be closed.

It should be understood that the cooking compartment may be divided by a baffle into a standard baking and a standard broiling compartment. Further, the heating compartment may also serve as the broiler compartment for the oven with the heating compartment having a gas passageway substantially surrounding the cooking compartment for transfer of heat thereto. This is illustrated both in FIGS. 1 and 2, the burner 20 serving as the broiler burner for the broiler tray 23. During the baking cycle, baffle means between the cooking and heating compartment are open so that a portion of the combustion product can heat the cooking compartment directly. Conversely, during the self-cleaning cycle, the baffle means are closed with the oven operating as above described.

The invention has been described in detail with reference to particular and preferred embodiments thereof, but it will be understood that variations and modifications can be made within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

1. A self-cleaning gas-fired cooking oven which comprises: a cooking compartment; a heating compartment in heatexchanging relationship with said cooking compartment; a fuel gas burner disposed within said heating compartment; means for supplying fuel gas to said burner; means for supplying air to said heating compartment for combustion with said fuel gas to thereby heat said cooking compartment; means for exhausting combustion products from said heating compartment; means for aerating said cooking compartment; means for exhausting hot gases from said cooking compartment into said heating compartment to be mixed with the gases therein for complete incineration of combustible matter; and means for exchanging heat between said exhausted combustion products and said air supplied to said heating compartment to thereby preheat said air and cool said combustion products prior to discharging the same from said oven.

2. A self-cleaning oven according to claim I wherein said heating compartment also serves as the broiler compartment for said oven, and said heating compartment having gas passageway substantially surrounding said cooking compartment for transferring heat to the latter.

3. A self-cleaning oven according to claim I wherein said means for exchanging heat comprises a heat regenerator which includes a rotatably mounted heat sink means for serially contacting said exhausted combustion products and said air supplied to said heating compartment.

4. A self-cleaning oven according to claim I wherein said means for exchanging heat comprises a heat exchanger.

5. A self-cleaning oven according to claim 1 wherein aerating means comprises conduit means communicating between the exterior of said oven and said cooking compartment.

6. A self-cleaning oven according to claim 1 wherein said means for exhausting hot gases from cooking compartment comprises: conduit means communicating between said cooking compartment and said heating compartment; and aspirating means in said heating compartment at the terminus of said conduit means for aspirating gases from said cooking compartment.

7. A self-cleaning oven according to claim 1 wherein said means for exhausting hot gases from cooking compartment comprises conduit means communicating between said cooking compartment and said means for supplying air to said heating compartment.

8. A self-cleaning oven according to claim 1 further comprising: baffle means between said cooking and heating compartments; and means for closing said baffle means during cleaning cycle of said oven and for opening said baffle means during baking cycle of said oven so that a portion of the combustion products can heat said cooking compartment directly.

9. A method for cleaning a cooking oven which comprises:

passing fuel gas and air into a heating compartment in said oven for combustion thereat;

heating the cooking compartment in said oven with the heat from said combustion to vaporize the soil in said cooking compartment;

aerating said cooking compartment to remove vaporized soil therefrom;

passing'the aerated gases from the cooking compartment to the heating compartment and mixing the same with said air so that the vaporized soil will be incinerated; and

bringing said air supplied to said heating compartment into heat exchanging relationship with the combustion products prior to the latters discharge from the oven to thereby preheat said air and cool said combustion products.

10. A method according to claim 9 wherein said aerating step is carried out by admitting a controlled amount of ambient air into said cooking compartment.

11. A method according to claim 9 wherein the rate of passing fuel gas and air into said heating compartment is sufficient to heat said cooking compartment to a temperature at least about 750 F.

12. A method according to claim 9 wherein the rate of passing fuel gas and air into said heating compartment is sufficient to heat said cooking compartment to a temperature between about 850-1 l00 F.

13. A method according to claim 9 wherein said combustion products are cooled to about 230 F. before discharging from said oven.

14. A method according to claim 10 wherein the ratio of said aerating air supplied to said cooking compartment and said air supplied to said heating compartment is about 1:5. 

1. A self-cleaning gas-fired cooking oven which comprises: a cooking compartment; a heating compartment in heat-exchanging relationship with said cooking compartment; a fuel gas burner disposed within said heating compartment; means for supplying fuel gas to said burner; means for supplying air to said heating compartment for combustion with said fuel gas to thereby heat said cooking compartment; means for exhausting combustion products from said heating compartment; means for aerating said cooking compartment; means for exhausting hot gases from said cooking compartment into said heating compartment to be mixed with the gases therein for complete incineration of combustible matter; and means for exchanging heat between said exhausted combustion products and said air supplied to said heating compartment to thereby preheat said air and cool said combustion products prior to discharging the same from said oven.
 2. A self-cleaning oven according to claim 1 wherein said heating compartment also serves as the broiler compartment for said oven, and said heating compartment having gas passageway substantially surrounding said cooking compartment for transferring heat to the latter.
 3. A self-cleaning oven according to claim 1 wherein said means for exchanging heat comprises a heat regenerator which includes a rotatably mounted heat sink means for serially contacting said exhausted combustion products and said air supplied to said heating compartment.
 4. A self-cleaning oven according to claim 1 wherein said means for exchanging heat comprises a heat exchanger.
 5. A self-cleaning oven according to claim 1 wherein aerating means comprises conduit means communicating between the exterior of said oven and said cooking compartment.
 6. A self-cleaning oven according to claim 1 wherein said means for exhausting hot gases from cooking compartment comprises: conduit means communicating between said cooking compartment and said heating compartment; and aspirating means in said heating compartment at the terminus of said conduit means for aspirating gases from said cooking compartment.
 7. A self-cleaning oven according to claim 1 wherein said means for exhausting hot gases from cooking compartment comprises conduit means communicating between said cooking compartment and said means for supplying air to said heating compartment.
 8. A self-cleaning oven according to claim 1 further comprising: baffle means between said cooking and heating compartments; and means for closing said baffle means during cleaning cycle of said oven and for opening said baffle means during baking cycle of said oven so that a portion of the combustion products can heat said cooking compartment directly.
 9. A method for cleaning a cooking oven which comprises: passing fuel gas and air into a heating compartment in said oven for combustion thereat; heating the cooking compartment in said oven with the heat from said combustion to vaporize the soil in said cooking compartment; aerating said cooking compartment to remove vaporized soil therefrom; passing the aerated gases from the cooking compartment to the heating compartment and mixing the same with said air so that the vaporized soil will be incinerated; and bringing said air supplied to said heating compartment into heat exchanging relationship with the combustion products prior to the latter'' s discharge from the oven to thereby preheat said air and cool said combustion products.
 10. A method according to claim 9 wherein said aerating step is carried out by admitting a controlled amount of ambient air into said cooking compartment.
 11. A method according to claim 9 wherein the rate of passing fuel gas and air into said heating compartment is sufficient to heat said cooking compartment to a temperature at least about 750* F.
 12. A method according to claim 9 wherein the rate of passing fuel gas and air into said heating compartment is sufficient to heat said cooking compartment to a temperature between about 850*-1100* F.
 13. A method according to claim 9 wherein said combustion products are cooled to about 230* F. before discharging from said oven.
 14. A method according to claim 10 wherein the ratio of said aerating air supplied to said cooking compartment and said air supplied to said heating compartment is about 1:5. 